1. Field
This invention relates to a closure system for containers and more specifically a closure system on a container for medical liquid having an outer closure removeable by a cutting ring associated therewith.
2. Prior Art
Sterile medical liquids can be placed in thermoplastic containers and maintained in a bacteria-free condition prior to their use for irrigation of wounds or interior body cavities or for intravenous administration. Such containers generally have inner closures hermetically sealing off the contents of the container. Prior to use, however, the outer surfaces of these inner closures must be maintained in a sterile condition to avoid bacterial contamination when entry is made via the inner closures to deliver the sterile liquid. This can be accomplished by enclosing the inner closure with an outer closure which is sealed to the neck of the container. Outer closures can be removed by several means such as removal of a tear strip as disclosed in U.S. Pat. No. 3,394,831 or more recently by fracturing a line of weakness in the outer closure by stress imposed with a threaded jacking ring engaging the outer closure as disclosed in U.S. Pat. Nos. 3,923,183 and 3,945,525 for example. Such means for removing outer closures requires a degree of strength to effect rupture of the weakened zones which renders it difficult for certain medical personnel to use these closures.
Another approach to removing a plastic closure is by the use of cutting rings. In U.S. Pat. No. 3,266,658, there is disclosed a plastic container which is blow molded into a mold which contains a rigid ring with three cutting teeth projecting inwardly on the ring. Twisting the ring causes the teeth to sever the plastic circumferentially to provide an opening into the container. Such an approach would not be practicable in the manufacture of plastic containers having sterile liquids retained therein by inner closures. U.S. Pat. No. 3,591,031 shows a cutting ring fitted on the neck of a container which, in order to sever the neck portion, the ring would have to be squeezed while rotating it. This can be an awkward operation and one which may lead to non-uniform penetration of the plastic. In the arrangement in U.S. Pat. No. 3,784,045, while providing a more positive force on the cutting blade for severing the neck on a container, both the cutting ring and neck of the container must be threaded for the cutting action to take place.